AS June 2022 Q2
2.
| Activity | Immediately preceding activities |
|---|---|
| A | – |
| B | – |
| C | – |
| D | – |
| E | A |
| F | A, B, C |
| G | C |
| H | C |
| I | E |
| J | E, F, G |
| K | D, H |
Every activity shown in the precedence table has the same duration.
| Scheme | Marks | AO |
|---|---|---|
 | M1 A1 A1 A1 A1 | 1.1b 1.1b 1.1b 1.1b 1.1b |
| (5) |
Notes
Condone lack of, or incorrect, numbered events throughout. ‘Dealt with correctly’ means that the activity starts from the correct event but need not necessarily finish at the correct event, e.g. ‘K dealt with correctly’ requires the correct precedences for this activity, i.e. D and H labelled correctly and leading into the same node and K starting from that node but do not consider the end event for K. Activity on node is M0
If an arc is not labelled, for example, if the arc for activity D is not labelled (but the arc is present) then this will lose the first A mark and the final (CSO) A mark – they can still earn the third A mark on the bod. If two or more arcs are not labelled then mark according to the scheme. Assume that a solid line is an activity which has not been labelled rather than a dummy (even if in the correct place for where a dummy should be)
Ignore incorrect or lack of arrows on the activities for the first four marks only
M1: At least eight activities (labelled on arc), one start and at least two dummies placed
A1: Activities A, B, C, D, E, G and H dealt with correctly
A1: Activity F dealt with correctly and first two dummies & correct arrows dealt with correctly
A1: Activities I, J, K and final dummy dealt with correctly.
A1: cso All arrows present and correctly placed with one finish and no additional dummies
Please check all arcs carefully for arrows – if there are no arrows on any dummies then M1 only. Note that additional (but unnecessary) ‘correct’ dummies that still maintain precedence for the network should only be penalised with the final A mark if earned
| Scheme | Marks | AO |
|---|---|---|
| e.g. Activity E is preceded by activity A only, but activity F is preceded by activity B (and/or C) as well as activity A | B1 | 2.4 |
| (1) |
Notes
B1: Reference to E depends on A only, while F depends on A and B (and/or C). So must mention activities A, E, F and at least one of B and C
| Scheme | Marks | AO |
|---|---|---|
| Activity D as this is the only activity on a path from start to finish of which contains only two activities. All other activities appear on at least one longer path | M1 A1 | 3.1b 3.4 |
| (2) | ||
| (8 marks) |
Notes
M1: cao - Activity D only – if more than one activity stated then M0
A1: Correct reasoning. Explain that the path/route through D is the only one containing two activities or that all other routes/paths have 3 activities. Or mention activities C, H and K and that C and H together take ‘longer’ to finish than D